The serial number on a Johnson outboard motor indicates the year that the engine was manufactured. It can be determined by following a code that differs based on the year range in which the motor was built.
The label that usually contains the serial number is also called a nameplate.
The motor's model number is also marked on the nameplate, usually just below the serial number. The label can usually be found on the engine or its mounting bracket. Johnson has used an engine's model number to indicate year of production in different ways over the years. Based on year ranges, engine year information is found differently. For example, engines manufactured from 1980 to the present, have a two letter code (based on a key) at the end of the model number, that indicates the year they were produced. From 1969 to 1979, the two characters at the end of the model were the year in which the motor was built.